200 A alternator probably shot - but why, and what now ?

[AAVP7]

I just finished a body-off resto of my A0 Humvee and did a first test drive today. During the restoration, I swapped the 60 A for a brand new 200 A alternator. The 200 A is wired for dual voltage use, according to the TMs. I also compared and rechecked all the time with my A2 slantback, which has a 200A from the factory.
The new alternator is a Niehoff N1225-1 with a M3135 regulator.

Before the test drive, I had the engine running for about half an hour (for adjusting tranny oil, warming up, etc.). I also checked voltage at the regulator output posts before setting off, and got nice 28.8 and 14.5 volts, respectively. The voltage meter on the dash was at the top of the green. So everything looked fine. About 15 minutes into the drive, however, I noticed the voltage meter had dropped into the middle of yellow. I managed to get home, but again checking at the regulator output posts I got only 24.5 and 12.2 volts, which is exactly battery votage. So no more charging. I cycled the engine to see if the Niehoff overvoltage feature might have tripped, but got the same result.

I then ran all the tests in the Niehoff troubleshooting guide, and got the result that my regulator seems to be shot, but the external wiring and the alternator seem to be OK. I also checked all grounds, connections, etc.. All seem good.

Now my questions:

With the rather low battery voltages (24.5 / 12.2 V), I guess we can rule out that the regulator regards the batteries as "fully charged", and stops charging on purpose, right ?

Can the above voltages be already too low to excite the alternator enough ? I´m charging overnight, so will try with full batteries again.

Is it common for a regulator to fail after less than an hour of operation ? According to other posts, they seem to fail quite often, but right out of the box ?

How do I make sure that there are no external problems that killed the regulator ? The field coil resistance for example is supposed to be between 1.8 to 2.2 ohms according to Niehoff. I measured 2.8 ohms. Can this kill the next regulator ?

I know there are numerous 200 A threads (and I think I read them all). However, the price of new regulators has risen to such ridiculous levels that I thought I better ask a bit around before swapping a new one in just for a try.

Thanks in advance
Arnd

 

[Coug]

if you're seeing battery voltage at the regulator, then yes, it is unlikely the regulator stopped because it thinks the batteries are fully charged.
No, those voltages are not too low for the excitation circuit to work, so that shouldn't be the issue.

For the field col resistance, did you verify the resistance of the meter leads before testing, and subtract that from overall reading? I find it's not uncommon for leads to have half an ohm resistance, which would put your reading close enough to the expected range not to be an issue.

As for regulators, if you want a less expensive one for testing, TrailworthyFab sells used voltage regulators for $200, and I can verify that it IS the N3135 regulator for the 200 amp dual output system (I bought one 6 months back, works great)

Trail Worthy Fab :: Warning

(EDIT: Trailworthyfab no longer has them listed for sale on their website 2 years later)

 

[Mogman]

I was told the regulators are almost always the issue with the 200A, and that has been my experience (bought two non working 200A generators and both had bad regulators) so I carry a spare, only takes a few minuets to change, I would not be afraid of a used one as long as it is guaranteed to work.

 

[AAVP7]

Thanks for your replies, guys. That hint about the Trailworthy regulators is very interesting indeed.

My voltmeters´ leads are the original ones from the manufacturer, and are pre-compensated for. I always put the points together before the actual measurement to see if the meter shows zero. I sent an email to Niehoff to inquire about the 2.8 ohms; we´ll see if they reply.

Today, I started the truck again with fully charged batteries, just to make sure that the batteries are not the culprit. Same result, just battery voltage at the regulator outputs, and at the IGN input. So I´m pretty convinced now that the regulator is fried.

 

[AAVP7]

One addition to this: Niehoff did actually reply to my reqest, in a very detailed manner. Awesome company ! I wanted to share their hints here:

First, the range given for field coil resistance (1.8 to 2.2 ohms) in the troubleshooting manual was meant for room temperature. The resistance rises considerably with a hot alternator. So I took a new measurement on the cold alternator today, and got a nice 2.1 ohms.

Second, Niehoff confirmed that weak batteries over a long period can damage the regulator, as the field coil doesn´t magnetize fully, causing overheating of regulator components.

Third, and that surprised me a bit, Niehoff said that these regulators like a considerable "minimum load of at least 30 A on the 28 V side, especially with a high load on the 14 output".
A normal Humvee in civilian use even with all lights on will maybe draw about 30 A. Without lights, there is hardly any current at all.

 

[Retiredwarhorses]

I own no less than 13 trucks, all with 200’s...I’ve never had a bad 200amp generator in my shop...NEVER, I’ve had numerous bad regulators, as a matter of fact, I have a stack of bad ones, all of which did something different When they failed.

 

[NDT]

Niehoff really needs to step up their game. No reason for their products to be so unreliable. Similar problems on FMTVs.

 

[Retiredwarhorses]

Niehoff really needs to step up their game. No reason for their products to be so unreliable. Similar problems on FMTVs.

jump starting kills EESS boxes and voltage regulators....the military is well aware of it.

 

[Mogman]

if you're seeing battery voltage at the regulator, then yes, it is unlikely the regulator stopped because it thinks the batteries are fully charged.
No, those voltages are not too low for the excitation circuit to work, so that shouldn't be the issue.

For the field col resistance, did you verify the resistance of the meter leads before testing, and subtract that from overall reading? I find it's not uncommon for leads to have half an ohm resistance, which would put your reading close enough to the expected range not to be an issue.

As for regulators, if you want a less expensive one for testing, TrailworthyFab sells used voltage regulators for $200, and I can verify that it IS the N3135 regulator for the 200 amp dual output system (I bought one 6 months back, works great)

Trail Worthy Fab :: Warning

I have purchased bead locks and some 24 bolt wheels from those folks, have always been happy with them.

 

[Mogman]

jump starting kills EESS boxes and voltage regulators....the military is well aware of it.

That's one of the problems, and should not be, I have been jump starting vehicles for 50 years and have never seen a vehicle that it is just a crap shoot if it gets screwed up by simply jumping it off..

 

[mechanicjim]

That's one of the problems, and should not be, I have been jump starting vehicles for 50 years and have never seen a vehicle that it is just a crap shoot if it gets screwed up by simply jumping it off..

When you jump a "dead" set of batteries in a 24v truck each maintenance free battery can draw up to 40amps for AGM it can be upwards of 100amps. so if i jump a HMMWV with 4 dead maintenance/maintenance free battery's the draw can be upwards of 160amps just to feed the battery's for 30-45 mins.
If you look at how the alternator outputs based on its curve a N1225 has about 140amps at idle(28V side no 14V load). so if you are going to jump a vehicle you should run it at high idle or just floor the thing for 30mins.
If you don't want to run your engine at redline for 30-45 mins, then why would you do the same to your alternator?

Jumping causes alternator overload which in turn causes voltage fluctuations, which modern sensitive electronics don't like. Remember the batteries are the electrical system shock absorber when they are low of voltage they don't absorb the spikes as well.
And your running excessive heat thru the alternator /regulator the latter is only passively cooled by airflow in engine bay. which if you just jumped a vehicle and let it sit isn't very much.

 

[NDT]

When you jump a "dead" set of batteries in a 24v truck each maintenance free battery can draw up to 40amps for AGM it can be upwards of 100amps. so if i jump a HMMWV with 4 dead maintenance/maintenance free battery's the draw can be upwards of 160amps just to feed the battery's for 30-45 mins.
If you look at how the alternator outputs based on its curve a N1225 has about 140amps at idle(28V side no 14V load). so if you are going to jump a vehicle you should run it at high idle or just floor the thing for 30mins.
If you don't want to run your engine at redline for 30-45 mins, then why would you do the same to your alternator?

Jumping causes alternator overload which in turn causes voltage fluctuations, which modern sensitive electronics don't like. Remember the batteries are the electrical system shock absorber when they are low of voltage they don't absorb the spikes as well.
And your running excessive heat thru the alternator /regulator the latter is only passively cooled by airflow in engine bay. which if you just jumped a vehicle and let it sit isn't very much.

As said, the Niehoff regulators are what burn out, not the actual alternator. The regulator sees no high current. And the crappy HMMWV start boxes are not involved with charging current either.

 

[Mogman]

As said, the Niehoff regulators are what burn out, not the actual alternator. The regulator sees no high current. And the crappy HMMWV start boxes are not involved with charging current either.

The rest of the automotive industry has figured out how to protect the alternator from overload, Humvee's are not the only vehicle to suffer from dead batteries. AGM or otherwise

 

[frank8003]

jump starting kills EESS boxes and voltage regulators....the military is well aware of it.

G503 Military Vehicle Message Forums - Login

 

[Milcommoguy]

CAMO that me

 

[rolling18]

Just to jump in here... Nice afternoon and completed another NOT so smart boxes. Four hour build, 150 bucks for new parts. Wire sure went up $$

NO off shore parts. Can't say the "C" word anymore, CAMO

View attachment 830652
General layout


View attachment 830651
Ready to button it up

what's C.A.M.O?
can't seem to find it on google! heh
sent you a P.M too..

 

[Coug]

what's C.A.M.O?
can't seem to find it on google! heh
sent you a P.M too..

the guy you just responded to is "Camo" and makes an aftermarket replacement for the smart box

 

[rolling18]

the guy you just responded to is "Camo" and makes an aftermarket replacement for the smart box

HAHAH i have seen it many times on here and i thought it was an acronym!!! uhhh!!! grr

 

[TOBASH]

First name Cam. Last initial O.

 

[phemer]

So - Similar issue I'd love some guidance on.

My truck has the Niehoff N-1225-1 200A and a N3135 regulator.

When I start the truck, charges as normal then creeps to overcharge (mid-red on gauge) then upon blipping throttle, spikes past red limit. 30 seconds of this, battery guage drops between green and yellow.

I tested both poles on regulator/gennie. The 14v pole begins at 12.5 (battery level), upon starting, jumps to a healthy 14ish for 15-20 seconds, slowly creeps to 16v then spikes to 18v upon throttle for 10ish seconds before dropping to battery level (12.5). I tested the red pole on top of gennie. Same. Begins at 25.5ish, starts then jumps to 28.8ish, begins to creep to 30 then spikes to 32 before returning to 25.5ish.

So much conflicting info. Any idea how to diagnose the culprit between the gennie and the voltage regulator? I'd love not to use expensive trial and error.

Any guidance would be appreciated massively.